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sys/boot/mips/uboot/start.S
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| /*- | |||||
| * Copyright (c) 2016 Stanislav Galabov | |||||
| * All rights reserved. | |||||
| * | |||||
| * Redistribution and use in source and binary forms, with or without | |||||
| * modification, are permitted provided that the following conditions | |||||
| * are met: | |||||
| * 1. Redistributions of source code must retain the above copyright | |||||
| * notice, this list of conditions and the following disclaimer. | |||||
| * 2. Redistributions in binary form must reproduce the above copyright | |||||
| * notice, this list of conditions and the following disclaimer in the | |||||
| * documentation and/or other materials provided with the distribution. | |||||
| * | |||||
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND | |||||
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |||||
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |||||
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE | |||||
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |||||
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |||||
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |||||
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |||||
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |||||
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |||||
| * SUCH DAMAGE. | |||||
| * | |||||
| * $FreeBSD$ | |||||
| */ | |||||
| #include <machine/asm.h> | |||||
| .text | |||||
| #ifdef SUPPORT_SELF_RELOC | |||||
| .extern _C_LABEL(self_reloc) | |||||
| #endif | |||||
| .extern _C_LABEL(main) | |||||
| .weak _DYNAMIC | |||||
| /* | |||||
| * Entry point to the loader that U-Boot passes control to. | |||||
| */ | |||||
| ENTRY(_start) | |||||
| #ifdef SUPPORT_SELF_RELOC | |||||
| /* XXX: Does anyone need this part at all? It currently doesn't work. */ | |||||
| .set mips32r2 | |||||
| /* | |||||
| * Do self-relocation when the weak external symbol _DYNAMIC is non-NULL | |||||
| * When linked as a dynamic relocatable file, the linker automatically | |||||
| * defines _DYNAMIC with a value that is the offset of the dynamic | |||||
| * relocation info section. | |||||
| * Note that we're still on u-boot's stack here, but the self_reloc | |||||
| * code uses only a couple dozen bytes of stack space. | |||||
| */ | |||||
| lw t0, .here_off /* .here_off is a symbol whose value */ | |||||
| /* is its own offset in the text seg. */ | |||||
| /* Get its pc-relative address and */ | |||||
| lw t1, .dynamic_off /* subtract its value and we get */ | |||||
| nop | |||||
| add t2, t0, t1 | |||||
| movn t1, t2, t1 | |||||
| beqz t1, 1f | |||||
| nop | |||||
| b _C_LABEL(self_reloc) /* Do reloc if _DYNAMIC is non-NULL. */ | |||||
| nop | |||||
| 1: | |||||
| #endif | |||||
| sw sp, uboot_address | |||||
| b main | |||||
| END(_start) | |||||
| #ifdef SUPPORT_SELF_RELOC | |||||
| /* | |||||
| * Data for self-relocation, in the text segment for pc-rel access. | |||||
| */ | |||||
| .here_off: | |||||
| .word . - _start | |||||
| .dynamic_off: | |||||
| .word _DYNAMIC | |||||
| #endif | |||||
| /* | |||||
| * syscall() | |||||
| */ | |||||
| ENTRY(syscall) | |||||
| sw ra, ret_address | |||||
| lw t9, syscall_ptr | |||||
| jalr t9 | |||||
| nop | |||||
| lw ra, ret_address | |||||
| jr ra | |||||
| nop | |||||
| END(syscall) | |||||
| /* | |||||
| * Data section | |||||
| */ | |||||
| .data | |||||
| .align 4 | |||||
| .globl syscall_ptr | |||||
| syscall_ptr: | |||||
| .long 0 | |||||
| .globl uboot_address | |||||
| uboot_address: | |||||
| .long 0 | |||||
| ret_address: | |||||
| .long 0 | |||||